Nine investigators from three campuses of the University of Maryland seek funding for a Beckman Coulter Optima XL-I analytical ultracentrifuge. The user's group consists of Drs. Beckett (P1), Davis, Isaacs, Julin, Kahn, Munoz, and Greer from the Departments of Chemistry & Biochemistry and Chemical Engineering and the Center for Biological Structure & Organization at UMCP, Dr. David Weber from the Department of Biochemistry and Molecular Biology at the University of Maryland, Baltimore and Dr. Michael Summers from the HHMI and Department of Chemistry & Biochemistry, University of Maryland, Baltimore County. The centrifuge will be used for research in three general areas including analysis of macromolecular assembly in systems of biological interest, determination of the assembly properties of peptides and proteins for folding and high resolution structural studies, and characterization of the energetics and stoichiometries of synthetic biomimetic assemblies. Specific projects include determination of the energetics and stoichiometries of protein-protein interactions in transcriptional regulation and DNA recombination and repair, analysis of model ion channels, and determination of the assembly properties of model peptides for folding studies. The versatility provided by the absorption and interference optics of the Beckman Optima XL-I analytical ultracentrifuge will be essential to the success of the broad range of applications described in this proposal.